Computers

How to load data into partitioned table in hive?

  1. Create another table without partition.
  2. Load data into the table (Assume state is at first column).
  3. Insert into the partitioned table by selecting columns from the non-partitioned table (make sure you select state at the end).

How do I load data into a partitioned table?

  1. Load data simply copies data, it doesn’t read it so it cannot figure out what to partition.
  2. Would suggest that you load data into an intermediate table first (or using an external table pointing to all the files) and then letting partition dynamic insert to kick in to load it into a partitioned table.

How do I load data into a dynamic partitioned table in Hive?

For dynamic partitioning, you have to use INSERT … SELECT query (Hive insert). Inserting data into Hive table having DP, is a two step process. Create staging table in staging database in hive and load data into that table from external source such as RDBMS, document database or local files using Hive load.

How will you insert data from non-partitioned table to partitioned table in Hive?

You can use this command to create that: hive> INSERT INTO TABLE Y PARTITION(state) SELECT * from X; Here you should ensure that the partition column is the last column of the non-partitioned table.

How do I see the partitions on a Hive table?

  1. [db_name.] : Is an optional clause. This is used to list partitions of the table from a given database.
  2. [PARTITION(partition_spec)] : Is an optional clause. This is used to list a specific partition of a table.

Can we create partition on existing table in Hive?

You cannot change the partitioning scheme on a table in Hive. This would have to rewrite the complete dataset since partitions are mapped to folders in HDFS.

How dynamic partitions are added to Hive managed table?

You can configure Hive to create partitions dynamically and then run a query that creates the related directories on the file system, such as HDFS or S3. Hive then separates the data into the directories. Put the CSV file on a file system, for example in HDFS at /user/hive/dataload/employee , and change permissions.

What are the optimization techniques in Hive?

  1. Partitioning Tables: Hive partitioning is an effective method to improve the query performance on larger tables.
  2. De-normalizing data:
  3. Compress map/reduce output:
  4. Map join:
  5. Input Format Selection:
  6. Parallel execution:
  7. Vectorization:
  8. Unit Testing:

What is dynamic partitions in Hive?

Hive Dynamic Partitioning. Single insert to partition table is known as a dynamic partition. Usually, dynamic partition loads the data from the non-partitioned table. Dynamic Partition takes more time in loading data compared to static partition.

How manually insert data in Hive table?

  1. Step 1: Start all your Hadoop Daemon start-dfs.sh # this will start namenode, datanode and secondary namenode start-yarn.sh # this will start node manager and resource manager jps # To check running daemons.
  2. Step 2: Launch hive from terminal hive.
  3. Syntax:
  4. Example:
  5. Command:
  6. INSERT Query:

How do I merge two tables in hive?

  1. INNER JOIN – Select records that have matching values in both tables.
  2. LEFT JOIN (LEFT OUTER JOIN) – Returns all the values from the left table, plus the matched values from the right table, or NULL in case of no matching join predicate.

What is the difference between partitioning and bucketing a table in hive?

Hive partitioning is a technique to organize hive tables in an efficient manner. Based on partition keys it divides tables into different parts. … Bucketing is a technique where the tables or partitions are further sub-categorized into buckets for better structure of data and efficient querying.

How do I see the latest partition in Hive?

select max(ingest_date) from db. table_name; This would give me the expected output.. but kill the whole point of having partitions in the 1st place.

How do I see partitions in Linux?

  1. fdisk (fixed disk) Command.
  2. sfdisk (scriptable fdisk) Command.
  3. cfdisk (curses fdisk) Command.
  4. Parted Command.
  5. lsblk (list block) Command.
  6. blkid (block id) Command.
  7. hwinfo (hardware info) Command.

What is default Metastore in Hive?

The default value of this property is jdbc:derby:;databaseName=metastore_db;create=true. This value specifies that you will be using the embedded Derby as your Hive metastore, and the location of the metastore is metastore_db. We can also configure the directory for the Hive to store table information.

Can I partition an existing table?

The ALTER TABLE… ADD PARTITION command adds a partition to an existing partitioned table. There is no upper limit to the number of defined partitions in a partitioned table. New partitions must be of the same type (LIST, RANGE or HASH) as existing partitions.

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